Patch "staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
staging-vt6655-vnt_tx_packet-correct-tx-order-of-owned_by_nic.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Malcolm Priestley <[email protected]>
Date: Tue, 21 Apr 2015 22:33:00 +0100
Subject: staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC

From: Malcolm Priestley <[email protected]>

commit d65d2b25d2761153390df8026cca1a528d9b6c5a upstream.

The state of m_td0TD0.f1Owner should change after the buff_addr has been filled otherwise the device grabs the buffer too early.

m_td0TD0.f1Owner is protected by memory barriers on both sides of change.

iTDUsed is best incremented after MACvTransmit.

It appears that f1Owner actually polls to do the memory transfer.

A back port patch will be needed for v3.19

---
 drivers/staging/vt6655/device_main.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

@@ -1203,14 +1203,6 @@ static int vnt_tx_packet(struct vnt_priv
 	if (dma_idx == TYPE_AC0DMA)
 		head_td->pTDInfo->byFlags = TD_FLAGS_NETIF_SKB;
 
-	priv->iTDUsed[dma_idx]++;
-
-	/* Take ownership */
-	wmb();
-	head_td->m_td0TD0.f1Owner = OWNED_BY_NIC;
-
-	/* get Next */
-	wmb();
 	priv->apCurrTD[dma_idx] = head_td->next;
 
 	spin_unlock_irqrestore(&priv->lock, flags);

@@ -1231,11 +1223,18 @@ static int vnt_tx_packet(struct vnt_priv
 
 	head_td->buff_addr = cpu_to_le32(head_td->pTDInfo->skb_dma);
 
+	/* Poll Transmit the adapter */
+	wmb();
+	head_td->m_td0TD0.f1Owner = OWNED_BY_NIC;
+	wmb(); /* second memory barrier */
+
 	if (head_td->pTDInfo->byFlags & TD_FLAGS_NETIF_SKB)
 		MACvTransmitAC0(priv->PortOffset);
 	else
 		MACvTransmit0(priv->PortOffset);
 
+	priv->iTDUsed[dma_idx]++;
+
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	return 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/staging-vt6655-vnt_tx_packet-correct-tx-order-of-owned_by_nic.patch queue-4.0/staging-vt6655-device_free_tx_buf-use-only-ieee80211_tx_status_irqsafe.patch queue-4.0/staging-vt6656-use-ieee80211_tx_info-to-select-packet-type.patch queue-4.0/staging-vt6655-implement-ieee80211_tx_stat_noack_transmitted.patch queue-4.0/staging-vt6655-fix-80211-control-and-management-status-reporting.patch queue-4.0/staging-vt6655-lock-macvwritebssidaddress.patch